Ported sub treatment system

ABSTRACT

A ported sub treatment system in which well treatment materials are pumped into an uncased portion of a well through a pipe having a number of holes at specific locations along its length such that these materials are able to be distributed as desired by the operator, through these holes, along the length of the well. The treatment system is also able to provide sufficient pressure such that treatment materials are able to penetrate or fracture the rock surrounding the well, if necessary.

BACKGROUND OF THE INVENTION

[0001] This application is a continuation-in-part of patent application No. 09/228,667, filed on Jan. 12, 1999.

[0002] Commonly, in the oil industry, it is necessary to treat wells with materials such as stimulation fluids. In certain stimulation processes, it is necessary for the fluids to be under enough pressure that they penetrate the rock surrounding the well, and that the fluids be dispersed at specific locations desired by the operator along the length of the well. This becomes especially necessary with horizontal wells, which can have very long uncased portions requiring stimulation. It is also necessary, when treating long, uncased portions of a well to use several “stages.” The most commonly used methods of well treatment are typically only able to treat, at most, a few hundred feet of a well at a time. If a longer treatment length is needed, the operator must stop the treatment process, move the tool, and begin pumping well treatment materials again. Each process of starting and stopping is a separate “stage.”

[0003] Traditionally, in the oil industry, two methods have been used to distribute treatment or stimulation materials into an uncased well. One method is the “bullhead” treatment method in which a jointed tubing is run to the bottom of the vertical or cased section of the well, and stimulation materials are pumped through the tubing, out of its bottom end, into the uncased portion of the well. This method has been successful in creating high enough pressures such that rock penetration, or “matrix acidizing” can be achieved, or the rock may be parted in a fracture treatment. However, studies have shown that this method offers very poor distribution of stimulation materials throughout the well, and does not allow the operator to determine where in the formation the stimulation materials are distributed or to treat long portions (i.e. over 100 feet) of the well during a single stage.

[0004] Another method that has been used is the coiled tubing method, wherein a thin coiled tubing is run down the length of the well as stimulation materials are pumped through the coiled tubing. This method offers very good distribution of stimulation materials, however the coiled tubing method typically does not provide enough flow rate and/or pressure such that the stimulation materials are able to adequately penetrate the matrix of, or fracture, the rock surrounding the well. The coiled tubing method is only able to “wash” the face of the formation. Also, as with the bullhead method, many stages (or continuous movement of the tubing) are needed to treat long portions of the well, as the coiled tubing method is generally only able to treat lengths of 20-50 feet of a well at any one point in time.

[0005] Another well stimulation system popular in the early 1980's was the “limited entry” system. This method was used exclusively with vertical, cased wells and involved perforating the casing at specific locations in the well. After a vertical well was completed with casing cemented in place, the casing was perforated in specific locations along its length and stimulation materials were pumped into the well. Thus, an operator could stimulate specific perforated portions of the vertical cased well. This method, however, did not allow any variance of the locations to be treated at a later time. The casing perforations were permanently in place, and if further locations were desired to be treated, the original perforations could not be removed without losing the pathway to the original treatment. The stimulated areas could only be added, not varied. Thus, repeated stimulation of the same cased, vertical well in different locations resulted in a reduction of the desired distribution. Also, the gross interval able to be treated by this system was typically limited to 200-400 feet, as in-situ stress variations precluded larger intervals from being treated in a single stage.

[0006] In uncased wells, the limited entry method is not available, especially when the uncased portion of the well is deviated. According to J. A. Short, author of Introduction to Directional and Horizontal Drilling, p. 215 (1993), fracturing and acidizing stimulation techniques are uncommon in horizontal open hole completions because “it is difficult to determine the amount and location where treating fluid enters the formation.” Thus, for the foregoing reasons, there is a need for an improved stimulation method for use with uncased wells, providing the operator with a sufficient ability to distribute stimulation materials at particular locations in the formation, or up to thousands of continuous feet of the formation, in a single stage, while also providing adequate pressure such that stimulation materials can penetrate the matrix of, or fracture, the rock if necessary.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to a process for providing stimulation or other materials, such as acidizing fluid, to the uncased portion of a well while providing a specifically desired distribution of the material along the well's length, as well as adequate pressure such that the stimulation materials can penetrate the matrix of, or even fracture, the rock if necessary. The specific distribution locations may then be easily varied and/or used with other wells. One exemplary method involves taking a normal jointed string of pipe (which can include production tubing, casing, or any other type of oilfield pipe) and inserting ported subs, which are portions of pipe with holes along their length, at calculated intervals along the tubing string's length, depending on what area of the formation is desired to be treated. These ported subs may be joints of typical production tubing, or other joints of pipe, which have openings along their length sufficient to release stimulation materials. Because production tubing or other heavy-duty oilfield pipe may be used, stimulation materials may be pumped into the well at a sufficient pressure such that the rock can be penetrated. Also, the distribution of holes along the pipe's length provides an opportunity for the stimulation materials to be deposited into the well at several calculated points along its length in a single stage. Alternatively, up to several thousand continuous feet of the well (including the entire uncased portion, if desired) can be treated in a single stage. The disclosed method thus provides a specifically desired distribution of stimulation materials along the length of the well without the requirement of multiple stages. The pipe can then be removed and the location of the ported subs changed such that a different desired distribution can be achieved with the same or a different well. Alternatively, the pipe can remain in the well for some period of time and serve as the production conduit.

[0008] Another exemplary embodiment, which one of ordinary skill in the art would understand is inherently disclosed in the description above and in the parent application, involves the “creation” of ported subs after the string of pipe is inserted into the well. This is done by inserting a pipe not having openings in its sides into the well, then, once inserted, perforating the pipe at specific, desired locations. Such methods of perforation are well known in the art. Once the desired perforations are in place, multiple (or very long) portions of the well may be treated in a single stage, as discussed above. The pipe may then be removed, so as to change the location of the ported subs and/or for reuse on another well. Again, alternatively, the pipe can remain in the well for some period of time and serve as the production conduit.

[0009] It is preferred, but not required, that in the disclosed method the bottom end of the pipe be plugged for maximum effectiveness. Also, if the well to be treated is one with a number of laterals originating from the same primary drilling hole, an inflatable packer can be placed at the top of the lateral being treated, after its kick off point from the central bore hole, such that the stimulation materials do not overflow into other laterals, and such that pressure is maintained in the lateral being treated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a cross sectional view of an illustrative embodiment of a ported sub treatment system.

[0011]FIG. 2 is a cross-sectional view of a ported sub having holes and nozzles of variable sizes.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0012] As shown in FIG. 1, one exemplary embodiment of this invention comprises a length of pipe 18, which is preferably jointed, having a plurality of holes 20 placed at specific intervals along its length. These holes may be placed before or after insertion into a well by several known methods, including machining holes into specific joints or portions of the pipe during the manufacturing process and post-insertion downhole perforation.

[0013] The holes 20 are of an effective size to release well treatment or stimulation materials, when such materials are pumped into the tubing. This jointed tubing string can be any type of pipe, preferably a type that is normally used in oilfield operations such as bullhead stimulation operations, or conventional production tubing, and may be of a type that can withstand high pressures. The material that this pipe is constructed of can be varied depending on what types of materials are being pumped into the well. It should be known by one of ordinary skill in the art what types of tubing can withstand the pressures of and be used with different types of well treatments, such as washing, fracturing, and acidizing.

[0014] The holes along the length of the tubing string can be provided by inserting ported subs 14, preferably jointed ported subs, containing one or more openings 20 along their length, at points along the pipe 18. These openings may be created either before or after inserting the pipe into the well, and are of sufficient size to release stimulation materials. The ported subs are preferably constructed of the same material as the pipe, however, any kind of oilfield pipe, such as normal carbon steel tubing or other similar tubing, should work sufficiently. The size of and/or number of the holes 20 will depend on the viscosity of the materials meant to be distributed throughout the well and can easily be determined by one of ordinary skill in the art. The hole size and/or number can also be varied depending on the desired volume of materials to be pumped into the well or the desired volume to be pumped out of each set of holes. Hole size, however, preferably ranges from about 0.125 inches to about 1 inch in diameter. In an embodiment in which the holes are post-insertion perforations, those of ordinary skill in the art know how to vary the size and/or number of the holes as necessary.

[0015] In another illustrative embodiment of this invention, as shown in FIG. 2, holes 20 are surrounded by nozzles 21 which may be replaceable, i.e., the nozzles can be removed and nozzles of other sizes and materials attached in their place. Plugs 22 can also be inserted instead of nozzles in order to reduce the number of holes, if desired. In this way, the hole size and number of holes in a ported sub can be predetermined and varied for use with different types of well treatment fluids. Nozzles 21 may preferably be made of a non-erosional (non-corrosive) material such as tungsten carbide or any other material that resists being destroyed by the well treatment materials that can be utilized with this system. Different sizes of nozzles 21 may also be utilized in the same or different ported subs 14 during each well treatment such that pressure and/or distribution of well treatment fluids can be varied throughout different sections of the uncased portion of the well being treated.

[0016] In a preferred embodiment, the bottom end of the pipe 18 may be plugged (such as with plug 40) such that no treatment materials can travel through the open end of the pipe. Therefore, all materials must be released from the pipe through holes 20 along its length.

[0017] An embodiment of the invention can also be used when the well being treated is one of a plurality of lateral wells, or “laterals.” A “lateral” is one of several deviated or horizontal wells originating from the same central well. This is shown in FIG. 1. In this situation, an inflatable or other type of packer 28 may be utilized to prevent spillage of treatment materials into the other laterals 34, as shown in FIG. 1. The packer 28 can be placed at the top of the lateral being treated, at a distance below the location at which the lateral deviates from the central well 30. This location is known as the “kick off point.” It should be remembered, however, that this material may be used with any uncased well, whether deviated or vertical.

[0018] In another illustrative embodiment, ported subs 14 containing a plurality of holes 20, are placed at various points along the length of a pipe, either before or after insertion of the pipe into a well. The specific placement of ported subs 14 may depend on the length of the uncased portion of the well sought to be treated as well as the particular distribution of treatment materials desired by the operator. As discussed above, a benefit of the disclosed method is the ability to treat very long portions of the well, if desired, in a single stage. Thus, the distribution of materials may range from the treatment of multiple lengths of only several hundred feet of well, to treatment of one or more very long sections of a well (i.e. over 1000 feet), to treatment of the entire uncased wellbore, in a single stage. One of ordinary skill in the art should be able to calculate the specific location of the ported subs resulting in the desired distribution of materials.

[0019] Ported subs 14 are preferably jointed so that they may be easily connected at selected points along the pipe 18. The number and location of ported subs 14 placed along the pipe 18 may affect both the distribution and pressure at which the materials are distributed into the well. Thus, the more ported subs or holes used will increase the distribution area. These factors, along with the size of the holes 20 and nozzles 21 (if used) in ported subs 14 should give a skilled operator the ability to easily achieve the desired distribution of treatment materials in the well. Also, the number of holes 20 used and their placement along the pipe 18 will vary depending on the particular well, field, and formation, as well as other factors unique to the particular well being treated. One of ordinary skill in the art may vary these factors to achieve the most effective treatment system for the particular well.

[0020] In an embodiment of the claimed method, the pipe 18, with ported subs 14, is inserted into the uncased well's production zone as far as desired. The “production zone” of the well is the area in which oil and/or gas enters the well. This area can be deviated or horizontal, relative to the earth's surface, as shown in FIG. 1. In horizontal operations, the production zone can often be several hundred or thousands of feet long. Those of ordinary skill in the art would also understand that the disclosed method can be used effectively when the ported subs 14 are placed in the pipe 18 after the pipe is inserted into the well by blowing perforations into specific portions of the pipe.

[0021] Materials, such as acidizing stimulants, proppent materials, or other well treatment materials, are then pumped or otherwise inserted into the pipe at the desired rate and pressure. These materials then exit the tubing at specific points in the wells' length out of the holes 20 in the ported subs 14. This results in improved distribution of the materials at the rate and pressure desired by the operator. Rates and pressures can be varied based on whether the operator desires to wash the sides of the well, merely penetrate the matrix of the rock, or cause fracturing of the rock itself. The pipe 18 can then be removed from the well and the location of ported subs 14 varied for use in treating another well. Alternatively, the pipe can remain in the well for some period of time and serve as the production conduit. Although this method is preferably used with horizontal wells, it can also be used with uncased portions of vertical or deviated wells.

[0022] If the well being treated is one of several laterals originating from a central well 30, the operator can prevent spillage of treatment materials into other laterals 34 by placing an inflatable packer 28, known to those of ordinary skill in the art, at a point in the lateral being treated after its kick off point from the central well. Therefore, desired distribution and high pressures are maintained while preventing stimulation materials from overflowing into other laterals.

[0023] This invention therefore allows an operator to treat significant lengths of the uncased portions of horizontal, vertical, or deviated wells in a single stage at a pressure sufficient to penetrate the matrix of, or fracture, the rock if necessary. However, it also allows the operator greater control over the distribution of stimulation materials along the length of the well, and at higher rates and pressures, than previous treatment systems have allowed, and reduce the costs, risks, and complexity of these types of treatments.

[0024] One exemplary embodiment of the disclosed invention is a method of providing materials to an uncased portion of a well comprising inserting an effective length of pipe into the uncased well, wherein the length of pipe has one or more holes located at multiple predetermined locations along the pipe's length, each location laterally spaced from the other and defined by a set of holes, and the pipe is not cemented into the well, and providing well treatment materials into the pipe such that the materials are released from the openings into predetermined locations within an uncased area of the well such that separate locations in the well proximate to each set of holes may be treated by the same well treatment materials in a single stage.

[0025] In one such embodiment, the uncased area of the well deviates from a direction perpendicular to the earth's surface. In another such embodiment, the length of pipe is jointed, and can comprise one or more ported subs placed at specific locations along the length of pipe, the ported subs comprising lengths of jointed pipe having one or more holes located along their length such that well treatment materials can be released from the holes. These holes may be surrounded by replaceable nozzles, which can be varied in size and/or non-erosional. In another such embodiment, the length of pipe is plugged at its bottom end.

[0026] In another such embodiment, a packer may be set at a location in the well such that the well treatment materials are effectively blocked from moving past the packer. In this situation, the well may be one of a plurality of lateral wells originating from a central bore hole and the packer is set at a location deeper than the kick-off point of the well. In another such embodiment the pipe can be left uncemented in the well after treatment.

[0027] Another exemplary embodiment of the disclosed invention is a well treatment device comprising a length of pipe having two ends and one or more holes located at multiple predetermined locations along the pipe's length, each location laterally spaced from the other and defined by a set of holes, such that well treatment materials can be released from the holes into an uncased portion of a well such that separate locations in the well proximate to each set of holes may be treated by the same well treatment materials in a single stage, the pipe not being cemented into the well, the device able to be reused on the same or different wells.

[0028] In one such embodiment, the length of pipe is jointed, and can comprise one or more ported subs placed at specific locations along the length of pipe, the ported subs comprising lengths of jointed pipe having one or more holes located along their length such that well treatment materials can be released from the holes. These holes may be surrounded by replaceable nozzles, which can be varied in size and/or non-erosional. In another such embodiment, the length of pipe is plugged at its bottom end. In another such embodiment, the ported subs can be removed from the locations along the length of pipe and replaced in different locations.

[0029] Another exemplary embodiment of the disclosed invention is a well treatment system comprising a length of pipe having two ends, and one or more openings at multiple predetermined locations along its length, each location laterally spaced from the other and defined by a set of holes, such that well treatment materials, when pumped into the pipe after the pipe has been inserted into an uncased portion of a well, are released from the openings at predetermined locations in the uncased portion of the well such that separate locations in the well proximate to each set of holes may be treated by the same well treatment materials in a single stage.

[0030] Another exemplary embodiment of the disclosed invention is a method of providing well treatment materials to an uncased portion of a well comprising inserting a length of pipe having a bottom end into the uncased well, wherein the pipe is not cemented into the well, and providing well treatment materials into the pipe such that the materials are released from a plurality of openings along the pipe's length into an uncased area of the well such that the entire uncased portion of the well may be treated in a single stage, the uncased portion being longer than 500 feet.

[0031] In one such embodiment, the uncased area of the well deviates from a direction perpendicular to the earth's surface. In another such embodiment, the length of pipe is jointed, and can comprise one or more ported subs placed at specific locations along the length of pipe, the ported subs comprising lengths of jointed pipe having one or more openings located along their length such that well treatment materials can be released from the openings. These openings may be surrounded by replaceable nozzles, which can be non-erosional. In another such embodiment, the length of pipe is plugged at its bottom end.

[0032] In another such embodiment, a packer may be set at a location in the well such that the well treatment materials are effectively blocked from moving past the packer. In this situation, the well may be one of a plurality of lateral wells originating from a central bore hole and the packer is set at a location deeper than the kick-off point of the well. In another such embodiment the pipe can be left uncemented in the well after treatment.

[0033] Another exemplary embodiment of the disclosed invention is a method of providing well treatment materials to an uncased portion of a well comprising inserting a length of pipe having a bottom end into the uncased well, wherein the pipe is not cemented into the well, and providing well treatment materials into the pipe such that the materials are released from a plurality of openings along the pipe's length into an uncased area of the well such that at least one uncased portion of the well longer than 500 feet may be treated in a single stage.

[0034] In one such embodiment, the uncased area of the well deviates from a direction perpendicular to the earth's surface. In another such embodiment, the length of pipe is jointed, and can comprise one or more ported subs placed at specific locations along the length of pipe, the ported subs comprising lengths of jointed pipe having one or more openings located along their length such that well treatment materials can be released from the openings. These openings may be surrounded by replaceable nozzles, which can be non-erosional. In another such embodiment, the length of pipe is plugged at its bottom end.

[0035] In another such embodiment, a packer may be set at a location in the well such that the well treatment materials are effectively blocked from moving past the packer. In this situation, the well may be one of a plurality of lateral wells originating from a central bore hole and the packer is set at a location deeper than the kick-off point of the well. In another such embodiment the pipe can be left uncemented in the well after treatment.

[0036] Another exemplary embodiment of the disclosed invention is a method of providing well treatment materials to an uncased portion of a well comprising inserting a length of pipe having a bottom end into the uncased well, wherein the pipe is not cemented into the well, perforating the pipe such that one or more openings are created at multiple locations along the pipe's length, each location laterally spaced from the other and defined by a set of holes, and providing well treatment materials into the pipe such that the materials are released from the openings into an uncased area of the well such that separate locations in the well proximate to each set of holes may be treated by the same well treatment materials in a single stage.

[0037] In one such embodiment, the uncased area of the well deviates from a direction perpendicular to the earth's surface. In another such embodiment, the length of pipe is jointed, and its openings may be surrounded by replaceable nozzles, which can be non-erosional. In another such embodiment, the length of pipe is plugged at its bottom end.

[0038] In another such embodiment, a packer may be set at a location in the well such that the well treatment materials are effectively blocked from moving past the packer. In this situation, the well may be one of a plurality of lateral wells originating from a central bore hole and the packer is set at a location deeper than the kick-off point of the well. In another such embodiment the pipe can be left uncemented in the well after treatment.

[0039] While the structures of the present invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to what has been described herein without departing from the concept and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention as it is set out in the following claims. 

What is claimed is:
 1. A method of providing well treatment materials to an uncased portion of a well comprising: inserting a length of pipe having a bottom end into said uncased well, wherein said pipe is not cemented into said well; and providing well treatment materials into said pipe such that said materials are released from a plurality of openings along the pipe's length into an uncased area of said well such that the entire uncased portion of the well may be treated in a single stage, said uncased portion being longer than 500 feet.
 2. The method of claim 1 in which the uncased area of said well deviates from a direction perpendicular to the earth's surface.
 3. The method of claim 1 wherein said length of pipe is jointed.
 4. The method of claim 3 wherein said length of pipe further comprises one or more ported subs placed at specific locations along said length of pipe, said ported subs comprising lengths of jointed pipe having one or more openings located along their length such that well treatment materials can be released from said openings.
 5. The method of claim 4 wherein said openings are surrounded by replaceable nozzles.
 6. The method of claim 5 wherein said nozzles are non-erosional.
 7. The method of claim 1 wherein said length of pipe is plugged at its bottom end.
 8. The method of claim 1 further comprising setting a packer at a location in said well such that said well treatment materials are effectively blocked from moving past said packer.
 9. The method of claim 8 wherein said well is one of a plurality of lateral wells originating from a central bore hole and said packer is set at a location deeper than the kick-off point of said well.
 10. The method of claim 1 further comprising leaving said pipe uncemented in said well after treatment.
 11. A method of providing well treatment materials to an uncased portion of a well comprising: inserting a length of pipe having a bottom end into said uncased well, wherein said pipe is not cemented into said well; and providing well treatment materials into said pipe such that said materials are released from a plurality of openings along the pipe's length into an uncased area of said well such that at least one uncased portion of the well longer than 500 feet may be treated in a single stage.
 12. The method of claim 11 in which the uncased area of said well deviates from a direction perpendicular to the earth's surface.
 13. The method of claim 11 wherein said length of pipe is jointed.
 14. The method of claim 13 wherein said length of pipe further comprises one or more ported subs placed at specific locations along said length of pipe, said ported subs comprising lengths of jointed pipe having one or more openings located along their length such that well treatment materials can be released from said openings.
 15. The method of claim 14 wherein said openings are surrounded by replaceable nozzles.
 16. The method of claim 15 wherein said nozzles are non-erosional.
 17. The method of claim 11 wherein said length of pipe is plugged at its bottom end.
 18. The method of claim 11 further comprising setting a packer at a location in said well such that said well treatment materials are effectively blocked from moving past said packer.
 19. The method of claim 18 wherein said well is one of a plurality of lateral wells originating from a central bore hole and said packer is set at a location deeper than the kick-off point of said well.
 20. The method of claim 11 further comprising leaving said pipe uncemented in said well after treatment.
 21. A method of providing well treatment materials to an uncased portion of a well comprising: inserting a length of pipe having a bottom end into said uncased well, wherein said pipe is not cemented into said well; perforating said pipe such that one or more openings are created at multiple locations along the pipe's length, each location laterally spaced from the other and defined by a set of holes; and providing well treatment materials into said pipe such that said materials are released from said openings into an uncased area of said well such that separate locations in said well proximate to each set of holes may be treated by the same well treatment materials in a single stage.
 22. The method of claim 21 in which the uncased area of said well deviates from a direction perpendicular to the earth's surface.
 23. The method of claim 21 wherein said length of pipe is jointed.
 24. The method of claim 21 wherein said openings are surrounded by replaceable nozzles.
 25. The method of claim 24 wherein said nozzles are non-erosional.
 26. The method of claim 21 wherein said length of pipe is plugged at its bottom end.
 27. The method of claim 21 further comprising setting a packer at a location in said well such that said well treatment materials are effectively blocked from moving past said packer.
 28. The method of claim 27 wherein said well is one of a plurality of lateral wells originating from a central bore hole and said packer is set at a location deeper than the kick-off point of said well.
 29. The method of claim 21 further comprising leaving said pipe uncemented in said well after treatment. 